1. Field of the Invention
The present invention relates to a control system of a motorcycle and a motorcycle including such a control system.
2. Description of the Related Art
Conventionally, front-and-rear-wheel steering systems have been developed that steer the rear wheel according to the steering of the front wheel of a motorcycle.
Some conventional front-and-rear-wheel steering systems have a mechanism that steers the rear wheel mechanically or electrically according to the steering angle of the front wheel (for example, see JP 61-160374 A, JP 2927477 B, and JP 3206610 B), and other systems have a mechanism that steer the rear wheel automatically according to a lateral force exerted on the rear wheel (for example, see JP 2829009 B and JP 7-98507 B).
However, when any one of the mechanisms disclosed in JP 61-160374 A, JP 2927477 B, JP 3206610 B, JP 2829009 B, and JP 7-98507 B is used, the stability of the motorcycle at the time of straight running is improved while the stability of the motorcycle at the time of turning is decreased.
In the front-and-rear-wheel steering system described in JP 2938911 B, for example, the steering amount of the rear wheel is changed between the high speed running and the low and middle speed running. This is intended to give the desired stability during straight running and stability during steering at high speed running and during the low and middle speed running, respectively. In addition, in the front-and-rear-wheel steering system described in JP 3200771 B, a speed, a yaw rate, a roll rate and the like are detected and the rear wheel is steered in phase with the steering direction of the front wheel based on the detection results. Thus, the vibration of the motorcycle during steering the rear wheel is damped.
Additionally, in the systems described in JP 2938911 B and JP 3200771 B, the steering angle of the rear wheel is determined based on that of the front wheel. In such a steering method, a large steering torque and a large roll angle are needed to turn the motorcycle in an unstable condition. For this reason, the drivability of the motorcycle decreases and stable turning cannot be performed in some cases.